1. Field of the Invention
The present invention relates to a method of separating nuts from kernels in a nut-and-kernel mixture. Such separation is difficult to be attained with recourse to difference in weight or color. The present invention effects a required separation in terms of different sounds produced by nuts and kernels when rolling or falling. In the specification and claims, the word "nut" means a nutmeat completely or partly surrounded by a shell. And the word "kernel" means nutmeat having no surrounding shell.
2. Description of Related Art
Foreign substances and poor quality nuts such as deformed or unmatured nuts are found in large amounts of almonds, cashew nuts, groundnuts, hazel nuts, pistachio nuts and other nuts, and are separated by hands. In the hope of saving tedious, laborious work a method of separating nuts from kernels in a nut-and-kernel mixture in terms of the optical reflecting characteristics is proposed for separation in Japanese Patent Publication 1-199683(A). Specifically, the proposed method uses the noted difference of reflective coefficients of nuts and kernels when exposed to the near infrared rays of 1,200 nm-long wavelength.
A method and apparatus of separating nuts from kernels in a nut-and-kernel mixture in terms of the distinctive spectral characteristics of reflecting rays is proposed for separation in Japanese Patent Publication 52-145277(A). Also, a method of separating beans of good quality from beans of poor quality in terms of their dynamic characteristics is proposed in Japanese Patent Publication 55-114375(A). Beans of good quality can be easily rolled. Beans of poor quality deformed by insect erosion, blight or immaturity are incomplete in shape (remote from spherical form), and therefore, such deformed pieces cannot be easily rolled.
The manual separation by sight has many problems, as for instance follows: the separating efficiency is low; the separating capability lowers with time; and the labor expense is high. The method of Japanese Patent Publication 55-114375(A) cannot be applied to the separation of nuts from kernels in case each nuts having good quality and also a thin shell surrounding a nutmeat because of little or no difference in rolling characteristics. As for the methods of Japanese Patent Publications 1-199683(A) and 52-145277(A), these proposed methods cannot be applied to hazel nuts and other nuts which show substantially same optical reflecting characteristics for shells and kernels, thus permitting no distinction therebetween with recourse to their reflecting characteristics. The shells and kernels of hazel nuts are hardly distinguishable in color even by sight, and therefore, it is most likely that nuts are overlooked and are present among kernels, and when such nuts are put in mouth and crushed by teeth, sometimes teeth are damaged by counter force of excessive strength.
There has been an ever increasing demand for automatically separating nuts from kernels in a nut-and-kernel mixture, particularly in case that nuts and kernels have same dynamic or optical characteristics.
The inventor discovered that nuts and kernels produce distinctive sounds characteristic of nuts and kernels, in terms of which nuts and kernels can be separated from each other. Specifically nuts when rolling or falling will produce a sound having an increased sound pressure in the range of about 6 to 16 kilohertz, whereas kernels when rolling or falling will produce little or no sound components in the same range.